class Mail::FieldList

def insert_field(field)

From
Licensed under
Copyright (C) 2001-2013 Python Software Foundation.
Heavily based on bisect.insort from Python, which is:

Insert the field in sorted order. 
def insert_field(field)
  lo, hi = 0, size
  while lo < hi
    mid = (lo + hi).div(2)
    if field < self[mid]
      hi = mid
    else
      lo = mid + 1
    end
  end
  insert lo, field
end